During her career she has been a participant of more than 15 plant collecting and exchange expeditions to locations including China, India, Italy, Japan, Portugal, Russia, and throughout the United States including Alaska and Hawaii. She was selected as Specialty Crop Curator for the US Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository in Corvallis, Oregon in 1987, and became Research Leader of that gene bank in 1989. In December 2009, she was asked to manage the Palmer, Alaska, Arctic and Subarctic Plant Gene Bank, in addition to that in Corvallis.  Dr. Hummer is an active member in the American Society of Horticultural Science, and was selected as a Fellow in 2006. She was the first woman president of the American Pomological Society (2004-2006), and has been the liaison between that society and the International Society for Horticultural Science to digitize valuable historical horticultural publications and provide them on-line for the benefit of all horticulturists. In 2006, she chaired the expert committee that developed the Global Conservation Strategy for Strawberry, co-sponsored by the Global Crop Diversity Trust. In 2009, she was recognized by the Sveriges Lantbruksuniversitet with an honorary doctorate in Agronomy. She is the author of more than 160 scientific journal papers, 13 chapters, and co-wrote or edited 8 books. She was the Chair of the Commission on Plant Genetic Resources for the International Society of Horticultural Science from 2002 to 2010 and was elected as Vice President of that Society in 2010.